The present invention relates to apparatus for applying caps to bottles especially those which are screwed on to a bottle or similar article. More particularly, the invention relates to improved chucks for use with existing screw capping machines.
There are a number of bottle capping machines currently used in applying screw caps onto bottles. In general, these machines employ a reciprocating mechanism to reciprocate a screw cap applying spindle assembly through a capping cycle. A screw cap chuck is attachable to the spindle assembly. The machines operate with a fixed and predetermined downward pressure and permit a predetermined twisting torque to be applied to the screw cap. Both the downward pressure and the torque are adjustable. Further, the machines are usually height adjustable to accommodate a range of bottle heights.
There are a number of applications for such machines where high speed production and controlled torque screw capping is required. One such application is in the pharmaceutical industry in which items such as dyes, stains, and culture media are packaged in screw cap bottles or screw cap test tubes which must be torqued to precise values.
The machines currently in use employ capping chucks (also referred to as capping shells) which form a generally cylindrical throat surface. The chucks are typically constructed of aluminum or similar light material and a resilient sleeve of rubber or similar material is insertable into the chuck throat. It is this resilient sleeve which actually contacts and grips the screw cap.
In high speed operation, this resilient sleeve is subject to rapid wear and deterioration. This can result in slippage so that the incorrect twisting torque is applied to the screw cap necessitating frequent readjustment of the torque setting. Additionally, as the sleeve deteriorates further, flaking off of the sleeve material can occur. This is unacceptable, especially in an application such as pharmaceutical packaging where an uncontaminated environment is required. Therefore, the resilient sleeve inserts in the capping chucks must be replaced frequently, resulting in high machine downtime and lower productivity.
Additionally, with this resilient sleeve, the amount of torque which can be applied to a bottle cap is limited before slippage of the cap against the sleeve insert occurs. The smaller the bottle cap diameter, the less torque can be applied through this resilient sleeve insert. This can be especially noticeable in applications such as pharmaceuticals where the bottle or test tube may have been exposed to heat in sterilizing procedures, which may in turn require that a higher torque value be applied to achieve secure screwing of the cap onto the bottle or tube.